Pattern matching
Pattern Matching
If we want to be able to allow people to dial through Asterisk and have Asterisk connect them to outside resources, we need a way to match on any possible phone number that the caller might dial. For situations like this, Asterisk offers pattern matching. Pattern matching allows you to create one extension in your dialplan that matches many different numbers. This is enormously useful.
Pattern-matching syntax. When using pattern matching, certain letters and symbols represent what we are trying to match. Patterns always start with an underscore (_). This tells Asterisk that we’re matching on a pattern, and not on an explicit extension name.
If you forget the underscore at the beginning of your pattern, Asterisk will think it’s just a named extension and won’t do any pattern matching. This is one of the most common mistakes people make when starting to learn Asterisk.
After the underscore, you can use one or more of the following characters:
X Matches any single digit from 0 to 9.
Z Matches any single digit from 1 to 9.
N Matches any single digit from 2 to 9.
[15-7] Matches a single character from the range of digits specified. In this case, the pattern matches a single 1, as well as any number in the range 5, 6, 7.
. (period) Wildcard match; matches one or more characters, no matter what they are.
If you’re not careful, wildcard matches can make your dialplans do things you’re not expecting (like matching built-in extensions such as i or h). You should use the wildcard match in a pattern only after you’ve matched as many other digits as possible. For example, the following pattern match should probably never be used:
_.
In fact, Asterisk will warn you if you try to use it. Instead, if you really need a catch-all pattern match, use this one to match all strings that start with a digit:
_X.
Or this one, to match any alphanumeric string:
_[0-9a-zA-Z].
! (bang) Wildcard match; matches zero or more characters, no matter what they are.
To use pattern matching in your dialplan, simply put the pattern in the place of the extension name (or number):
